package org.apache.lucene.store;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.HashSet;

/**
 * Expert: A Directory instance that switches files between
 * two other Directory instances.

 * <p>Files with the specified extensions are placed in the
 * primary directory; others are placed in the secondary
 * directory.  The provided Set must not change once passed
 * to this class, and must allow multiple threads to call
 * contains at once.</p>
 *
 * @lucene.experimental
 */

public class FileSwitchDirectory extends Directory {
    private final Directory secondaryDir;
    private final Directory primaryDir;
    private final Set<String> primaryExtensions;
    private boolean doClose;

    public FileSwitchDirectory(Set<String> primaryExtensions, Directory primaryDir, Directory secondaryDir, boolean doClose) {
        this.primaryExtensions = primaryExtensions;
        this.primaryDir = primaryDir;
        this.secondaryDir = secondaryDir;
        this.doClose = doClose;
        this.lockFactory = primaryDir.getLockFactory();
    }

    /** Return the primary directory */
    public Directory getPrimaryDir() {
        return primaryDir;
    }

    /** Return the secondary directory */
    public Directory getSecondaryDir() {
        return secondaryDir;
    }

    @Override
    public void close() throws IOException {
        if (doClose) {
            try {
                secondaryDir.close();
            } finally {
                primaryDir.close();
            }
            doClose = false;
        }
    }

    @Override
    public String[] listAll() throws IOException {
        Set<String> files = new HashSet<String>();
        // LUCENE-3380: either or both of our dirs could be FSDirs,
        // but if one underlying delegate is an FSDir and mkdirs() has not
        // yet been called, because so far everything is written to the other,
        // in this case, we don't want to throw a NoSuchDirectoryException
        NoSuchDirectoryException exc = null;
        try {
            for (String f : primaryDir.listAll()) {
                files.add(f);
            }
        } catch (NoSuchDirectoryException e) {
            exc = e;
        }
        try {
            for (String f : secondaryDir.listAll()) {
                files.add(f);
            }
        } catch (NoSuchDirectoryException e) {
            // we got NoSuchDirectoryException from both dirs
            // rethrow the first.
            if (exc != null) {
                throw exc;
            }
            // we got NoSuchDirectoryException from the secondary,
            // and the primary is empty.
            if (files.isEmpty()) {
                throw e;
            }
        }
        // we got NoSuchDirectoryException from the primary,
        // and the secondary is empty.
        if (exc != null && files.isEmpty()) {
            throw exc;
        }
        return files.toArray(new String[files.size()]);
    }

    /** Utility method to return a file's extension. */
    public static String getExtension(String name) {
        int i = name.lastIndexOf('.');
        if (i == -1) {
            return "";
        }
        return name.substring(i + 1, name.length());
    }

    private Directory getDirectory(String name) {
        String ext = getExtension(name);
        if (primaryExtensions.contains(ext)) {
            return primaryDir;
        } else {
            return secondaryDir;
        }
    }

    @Override
    public boolean fileExists(String name) throws IOException {
        return getDirectory(name).fileExists(name);
    }

    @Override
    public long fileModified(String name) throws IOException {
        return getDirectory(name).fileModified(name);
    }

    @Deprecated
    @Override
    /*  @deprecated Lucene never uses this API; it will be
     *  removed in 4.0. */
    public void touchFile(String name) throws IOException {
        getDirectory(name).touchFile(name);
    }

    @Override
    public void deleteFile(String name) throws IOException {
        getDirectory(name).deleteFile(name);
    }

    @Override
    public long fileLength(String name) throws IOException {
        return getDirectory(name).fileLength(name);
    }

    @Override
    public IndexOutput createOutput(String name) throws IOException {
        return getDirectory(name).createOutput(name);
    }

    @Deprecated
    @Override
    public void sync(String name) throws IOException {
        sync(Collections.singleton(name));
    }

    @Override
    public void sync(Collection<String> names) throws IOException {
        List<String> primaryNames = new ArrayList<String>();
        List<String> secondaryNames = new ArrayList<String>();

        for (String name : names)
            if (primaryExtensions.contains(getExtension(name)))
                primaryNames.add(name);
            else
                secondaryNames.add(name);

        primaryDir.sync(primaryNames);
        secondaryDir.sync(secondaryNames);
    }

    @Override
    public IndexInput openInput(String name) throws IOException {
        return getDirectory(name).openInput(name);
    }
}
